SPRINGFIELD -- MassMutual's net gain from operations before policyowner dividends and taxes - its primary earnings measure as a mutual company - rose 18 percent, to $1.85 billion in 2017.

MassMutual's net income doubled to $137 million, the Springfield-based insurance giant said on Tuesday.

"Fueled by a surging market performance and an improving global economy, MassMutual maintained its unwavering focus on serving its policyowners and customers, which drove our exceptional financial results in 2017," said Roger Crandall, MassMutual chairman, president and CEO in a news release. "Our diverse mix of high-performing businesses, outstanding financial strength, expanded advisor force and ongoing investments in enhancing our digital experience, all enabled us to reach more Americans in greater numbers last year, helping them secure their future and protect the ones they love."

MassMutual attributed the good financial news to a significant rise in its net investment income and favorable underwriting experience in its insurance business, meaning MassMutual was happy with the amount it paid out in insurance claims.

Sales of MassMutual whole life insurance reached $678 million, an increase of more than $20 million, marking the 12th consecutive year of record sales.

Total sales of all kinds of life insurance MassMutal sells were $752 million, up from more than $710 million last year, bringing the overall amount of life insurance protection the company provides to nearly $670 billion.

MassMutual said its workplace and institutional businesses combined to post more than $20 billion in sales, up 13 percent. this reflected growth in its workplace whole life, defined contribution investment only and defined benefit products.

It will pay $1.6 billion in dividends in 2018 to eligible participating policyowners - the 150th consecutive year the company will be paying a dividend.

MassMutual, number 77 on the Fortune magazine 500 in 2017, announced plans earlier this month for a major expansion in Massachusetts including a $300 million investment and 2,000 jobs to the Commonwealth over the next four years.

The insurance company has 3,000 employees in Springfield, where it was founded on May 15, 1851.